Novel Fluorescent Fluorene-Containing Conjugated Polymers: Synthesis, Photophysical Properties, and Application for the Detection of Common Bisphenols

Article abstract of DOI:10.1055/s-0037-1609946

Eight new fluorescent conjugated polymers were synthesized by the Suzuki polycondensation reaction of 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester and a conjugated dihalogenated monomer. The photophysical properties of these polymers were investigated as well-dissolved solutions in chloroform and as nanoparticle suspensions in water. Several of the polymers had large Stokes shifts (greater than 100 nm) and others demonstrated unique changes in the fluorescence properties in aggregated verse nonaggregated forms. Preliminary applications of these polymers in the detection of common bisphenols are also reported.

Full text of DOI:10.1055/s-0037-1609946

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Novel Fluorescent Fluorene-Containing Conjugated Polymers:
Synthesis, Photophysical Properties, and Application for the
Detection of Common Bisphenols
Daniel R. Jones
Ryan Vallee
Mindy Levine*
Department of Chemistry, University of Rhode Island,
140 Flagg Road, Kingston, 02881, USA
m_levine@uri.edu
Published as part of the Cluster Synthesis of Materials
Received: 16.07.2018
Accepted after revision: 13.08.2018
Published online: 20.09.2018
expected to provide architectures with the combined ad-
vantages of high signal-to-noise ratios and increased fluo-
rescence sensitivity.6
DOI: 10.1055/s-0037-1609946; Art ID: st-2018-r0450-c
Previous work in our group has focused on the use of
conjugated fluorescent polymers for the turn-on fluores-
cence detection of pesticides,7 for the turn-off (i.e. quench-
ing-based) fluorescence detection of nitroaromatics,8 and
for the highly sensitive detection of hydrogen peroxide via a
noncovalent, electrostatically driven anionic polymer–cat-
ionic titanium detection complex.9 All previously reported
studies in the Levine group used polymers that were either
commercially available or had been reported in the litera-
ture.10 None of these polymers had notable Stokes shifts,
and methods to achieve such large shifts by synthetic mod-
ification of the polymer architectures were relatively limited.
Many of the notable benefits of conjugated polymer-
based sensors are enhanced when the polymer is in an ag-
gregated state, such as nanoparticles. This enhancement is
due to the increased availability of interpolymer exciton
migration in addition to intra-polymer migration, resulting
in markedly more sampling of the analyte binding sites by
the generated excitons. Researchers have used the in-
creased sensitivity of conjugated polymer nanoparticles
(CPNs) for the detection of numerous analytes, including
pesticides,7 nitroaromatics,8 and cations11 at parts per bil-
lion (i.e. ppb) concentrations.12 This interest is driven by the
typically high fluorescence quantum yield of CPNs (~80%),3
low toxicity to biological systems,4 and ability to achieve
aggregation-induced emission of conjugated fluorescent
polymers when localized as nanoparticles.5 Additionally,
the modular design of conjugated fluorescent polymers and
the ability to control the size of CPNs by straightforward ex-
perimental manipulation provides a system that is highly
tunable and can be easily optimized.
Abstract Eight new fluorescent conjugated polymers were synthe-
sized by the Suzuki polycondensation reaction of 9,9-dioctylfluorene-
2,7-diboronic acid bis(1,3-propanediol) ester and a conjugated dihalo-
genated monomer. The photophysical properties of these polymers
were investigated as well-dissolved solutions in chloroform and as
nanoparticle suspensions in water. Several of the polymers had large
Stokes shifts (greater than 100 nm) and others demonstrated unique
changes in the fluorescence properties in aggregated verse nonaggre-
gated forms. Preliminary applications of these polymers in the detec-
tion of common bisphenols are also reported.
Key words polymers, nanostructures, aggregation, spectroscopy,
conjugation
The synthesis of conjugated fluorescent polymers with
extremely large (greater than 100 nm) Stokes shifts is of in-
terest for a broad variety of applications, including gas
sensing1 and biological imaging.2 Examples of fluorophores
with large Stokes shifts have been reported in the litera-
ture,3 and usually have charge-separated states3b or strong
donor–acceptor coupling3a that are responsible for such
large Stokes shifts. The practical advantage to large Stokes
shifts is that such shifts generally lead to high signal-to-
noise ratios as a result of the large separation between the
emission signal and the excitation wavelength. Less re-
search has focused on the synthesis and applications of
conjugated polymers with analogously large Stokes shifts,
with one reported example relying on the aggregation of a
conjugated polymer to enable such shifts.4 Nonetheless,
conjugated polymers are well-known for their high sensi-
tivity in fluorescence-based detection applications,5 and so
the ability to combine extremely large Stokes shifts with
the notable advantages of conjugated polymer chemistry is
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One family of analytes of particular interest as detection
targets is bisphenols. The most commonly used bisphenol is
Bisphenol A (BPA, compound 1), with over five million tons
of compound 1 manufactured worldwide per year.13 This
prevalence has led to a chronic detectable level of BPA in bio-
logical fluids (i.e. urine, blood, saliva) from the majority of
people living in developed nations.13 Such ubiquitous BPA
exposure is concerning, as BPA is a known estrogen mimic
and endocrine disruptor.14 Numerous studies have linked
chronic low dose exposure to BPA to numerous negative
health effects including prostate and breast cancer, obesity,
early onset puberty, and Type II diabetes.15 Regulatory
changes and consumer-driven pressure over the health ef-
fects of BPA have caused companies to replace BPA with
other bisphenols (BPs), such as bisphenol F (BPF, compound
2) and bisphenol S (BPS, compound 3).16 The structural sim-
ilarity and initial research on these BPs suggest that they
have similar or more severe negative health effects com-
pared to BPA, 1.16 Current methods for detecting BPs in-
clude gas chromatography coupled with mass spectrometry
(GC–MS),17 liquid chromatography coupled with mass spec-
trometry (LC–MS),18 and electrochemical techniques.19 GC–
MS and LC–MS techniques are costly and time-consuming,
while electrochemical techniques for the detection of bi-
sphenols require large overpotentials that damage elec-
trodes and reduce the system sensitivity and selectivity.20
Newer BPA detection methods,21 including chemilumines-
cent sensors,22 have also been reported.
Reported herein is the synthesis and photophysical
characterization of eight new fluorescent polymers and
their application for the fluorescence detection of common
BPs. The use of Suzuki coupling to synthesize conjugated
fluorescent polymers is well-precedented in the literature
to access a number of polymeric architectures,23 and has
significant advantages compared to other synthetic meth-
ods, including relative insensitivity to air and moisture,
high functional group tolerance, and generally high yields.24
Of the eight new architectures, four demonstrated Stokes
shifts greater than 100 nm, and three of the new polymers
had significantly different fluorescence responses based on
their level of aggregation. All polymers displayed some de-
gree of fluorescence changes with the addition of BPA, BPF,
or BPS (compounds 1–3, Figure 1), as both aggregated poly-
mer nanoparticles and well-dissolved polymer solutions.
Notably, 100% differentiation between the bisphenols was
observed using linear discriminant analysis of the resulting
fluorescence response signals.
O
S
OH
HO
HO
OH
O
H
H
BPA
1
BPS
3
HO
OH
BPF
2
Figure 1 Structures of bisphenol analytes
mer solubility in polar solvents. Undesired effects of incor-
porating sterically bulky or polar substituents include add-
ed synthetic challenges27 to access more functionalized
monomers, as well as difficulties in forming conjugated
polymer nanoparticles by hydrophobic collapse of the poly-
mer chain, as a result of the lower hydrophobicity of the
highly polar groups.28
Our fluorene containing polymers include only the two
solubilizing hydrocarbon side chains found on 9,9-dioctyl-
fluorene-2,7-diboronic acid bis(pinacol) ester (compound 4,
Scheme 1) and no solubilizing polar groups. A range of opti-
mized conditions from literature-reported studies29 were
employed in an attempt to increase polymer weight (Mn)
without increasing the number of solubilizing side chains.
Scheme 1 illustrates the general reaction used for the opti-
mization experiments, with the results of these experi-
ments summarized in Table 1. The use of palladium zero
complexes and tri(o-tolyl) phosphine ligands successfully
increased the weights (Mn) of the polymers, with the com-
bination of the two resulting in the second highest polymer
weight (Mn = 5000 g/mol). For P1, this molecular weight
corresponds to approximately 10 monomer units, and is
comparable to the molecular weights of some other conju-
gated polymers reported in the literature.10 Moreover, liter-
ature precedent indicates that the photophysical properties
of longer-chain conjugated polymers are comparable to
those of shorter-chain oligomers, with an oligomer of five
repeat units often displaying photophysical properties that
are indistinguishable from that of the full-length polymer.30
Finally, by removing ethanol and using the phase-transfer
catalyst tetra-n-butylammonium bromide (TBAB) with
tris(dibenzylideneacetone)dipalladium(0) and tri(o-tolyl)
phosphine as the ligand the highest polymer weight was
achieved (experiment number 11, Table 1).31
The photophysical and structural properties of all syn-
thesized polymers (Figure 2) were characterized as well-
dissolved solutions and as aggregated nanoparticles. Of
note, all polymers demonstrated measurable fluorescence
emission from excitation at or near the maximum absorp-
tion wavelength, with key results summarized in Table 2.
Polymer P1 has a large Stokes shift of over 200 nm and
is characterized by a relatively low molecular weight, likely
due to limitations on the solubility of the monomers and
polymer. Polymer P2 was designed to increase the polymer-
ic molecular weight while maintaining a large Stokes shift,
The solubility of conjugated polymers can pose prob-
lems in post-synthesis processing, as the propensity of the
conjugated chains to π-stack and aggregate leads to low sol-
ubility in most solvents. Options to enhance polymer solu-
bility include the incorporation of sterically bulky side
chains,25 which reduces aggregation, and the inclusion of
highly polar functional groups,26 which increases the poly-
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C8H17
C8H17
O
O
B
B
O
O
C8H17
4
+
K2CO3
50 °C, 72 h
O
C8H17
varied reaction conditions
see Table 1
O
n
Br
Br
P1
5
Scheme 1 Synthesis of P1
OC8H17
C8H17
O
C8H17
Ar
n
P1
P3
generic polymer structure
P4
C8H17
C8H17
C8H17
C8H17
O
C8H17
C8H17
co
n
m
C8H17O
P2
P5
P6
P7
O
C8H17
C8H17
C8H17
C8H17
O
C8H17
C8H17
co
n
m
O
O
P8
P9
Figure 2 Structures of newly synthesized polymers
similar to that of P1. This goal was achieved successfully by
increasing the number of alkyl-branched monomer units to
a 3:1 ratio of dioctylfluorene/fluorenone (Figure 2, P2) in a
random copolymer structure. This increased the polymer
weight (Mn) by a factor of approximately five (taking into
account the larger molecular weight of the monomer repeat
units) while still retaining the large Stokes shift observed in
P1 (Stokes shifts: P1 = 236 nm, P2 = 230 nm). Interestingly,
the random copolymer displayed an additional fluores-
cence emission peak with a smaller Stokes shift of 34 nm.
This peak (at 414 nm) matches the fluorescence emission of
poly-9,9-dioctylfluorene32 and the second peak (at 610 nm)
matches the fluorescence emission of 9-fluorenone.33
When P2 is aggregated as nanoparticles, the emission peak
at 414 nm disappears and the peak at 610 nm undergoes a
hypsochromic shift to 550 nm, (Figure 3), indicating energy
transfer from 9,9-dioctylfluorene monomer units (with
emission at 414 nm) to 9-fluorenone (with lower energy
emission). This energy transfer is facilitated in the aggre-
gated state because of facile interchain exciton migration
that is enabled in such architectures.
Polymer P3‘s UV absorbance and fluorescence emission
were visually similar to the spectra of polymers with signif-
icant amounts of dioctylfluorene units (P2 and P8). Howev-
er, P3 has a much higher quantum yield (0.7650) than P2
(0.0058) and P8 (0.0025), which is qualitatively similar to
the quantum yields of all fluorene conjugated polymers,
and has the smallest Stokes shift (33 nm) of all the investi-
gated polymers. The UV absorbance and fluorescence emis-
sion characteristics of P3 are of particular interest when
compared to polymer P4, as both P3 and P4 include fused
aromatic backbone segments in addition to their dioctylflu-
orene segments. However, their fused aromatic backbone
segments result in vastly different photophysical proper-
ties. Polymer P4 incorporates an unsubstituted anthracene
moiety into its polymer backbone, resulting in P4’s UV ab-
sorbance being similar to anthracene’s,34 which indicates
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Table 1 Summary of Reaction Optimization Experiments Using P1 as the Polymer Target
Exp.
Conditionsa
Resultsb
Catalyst and ligand
Monomer conc. (mol/L) Solvents
Mn (g/mol)
Mw (g/mol)
3800
PDI
1c
2
Pd(OAc)2 (0.15 mol equiv)
PPh3 (0.45 mol equiv)
0.033
0.033
0.022
0.033
0.033
0.033
0.033
0.033
0.010
0.005
0.033
1:1:1
2700
2600
2300
1800
4700
3200
2800
5000
3200
3100
5800
1.41
ethanol/toluene/water
Pd(OAc)2 (0.15 mol equiv)
PPh3 (0.45 mol equiv)
1:1:1
4200
3500
2100
5600
5400
3900
6500
4200
4400
8200
1.58
1.52
1.20
1.19
1.66
1.38
1.30
1.29
1.43
1.40
ethanol/toluene/water
3
Pd(OAc)2 (0.15 mol equiv)
PPh3 (0.45 mol equiv)
1:1
chloroform/water
4
Pd(OAc)2 (0.15 mol equiv)
PPh3 (0.45 mol equiv)
1:2
chloroform/water
5
Pd(PPh3)4 (0.15 mol equiv)
1:1:1
ethanol/toluene/water
6
Pd(OAc)2 (0.15 mol equiv)
P(o-Tol)3 (0.30 mol equiv)
1:1:1
ethanol/toluene/water
7
Pd2(dba)3 (0.15 mol equiv)
PPh3 (0.45 mol equiv)
1:1:1
ethanol/toluene/water
8
Pd2(dba)3 (0.15 mol equiv)
P(o-Tol)3 (0.30 mol equiv)
1:1:1
ethanol/toluene/water
9
Pd(PPh3)4 (0.15 mol equiv)
Pd(PPh3)4 (0.15 mol equiv)
1:1:1
ethanol/toluene/water
10
11
1:1:1
ethanol/toluene/water
Pd2(dba)3 (0.15 mol equiv)
P(o-Tol)3 (0.30 mol equiv)
TBAB (1 mol equiv)
1:1
toluene/water
a All reactions were heated at 50 °C for 72 h and used K2CO3 (3 mol equiv) as the base.
b All results were obtained on an Agilent 1260 Infinity II Multi-Detector GPC/SEC System with a polystyrene internal standard.
c Experiment 1 was heated at 111 °C for 72 h.
that the anthracene segment of P4 is absorbing more than
the dioctylfluorene segment. This is in contrast to P3,
which contains an unsubstituted naphthalene backbone
segment, but does not absorb at wavelengths typical of
naphthalene (311 nm).35 Furthermore, P4’s fluorescence
emission maximum is close to P3’s, resulting in a very large
Stokes shift (178 nm) for P4. These small structural changes
which result in large differences in the photophysical prop-
erties of the polymers demonstrate excellent tunability for
tailoring the polymer products for specific applications.
Table 2 Properties of Fluorescent Polymers P1–P9 Synthesized Using the Optimized Reaction Conditionsa
Polymer
Mn (g/mol)
Mw (g/mol)
PDI
UV λmax (nm) Stokes shift (nm)
Fluorescence emission (nm)
Quantum yieldb
Fl λmax
1
Fl λmax
2
λmax
1
λmax 2
P1
P2
P3
P4
P5
P6
P7
P8
P9
5000
26400
5300
3000
4800
6000
3200
21500
6700
6500
49300
14300
4200
1.30
374
380
378
262
345
341
374
377
353
236
34
–
610
–
0.0056
0.0068
0.7650
0.1403
0.8278
0.5918
0.9080
0.0025
0.3087
1.87
2.69
1.45
1.64
2.07
1.79
2.74
1.46
230
–
414
411
440
424
413
427
415
576
610
33
–
–
178
79
–
8000
102
95
75
287
–
447
436
449
664
–
12400
5700
72
53
59200
9800
38
223
a All reactions were heated at 50 °C for 72 h and used K2CO3 (3 mol equiv), Pd2(dba)3 (0.15 mol equiv), P(o-Tol)3 (0.30 mol equiv), and two monomers (1 mol
equiv each) at 0.033 mol/L in equal amounts ethanol, toluene, and water.
b Quantum yields were measured by using an integration sphere with the following references: 9,10-diphenylanthracene, quinine bisulfate, and 2-aminopyridine.
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Polymers P5 and P6 have similar photophysical proper-
ties, with UV absorbance maxima at 345 and 341 nm, re-
spectively. Both polymers have two fluorescence emission
maxima (P5 = 424, 447 nm; P6 = 414, 436 nm) and large
Stokes shifts (P5 = 79, 102 nm; P6 = 72, 95 nm). The differ-
ences in wavelength between the photophysical properties
of P5 and P6 are expectedly small as the structural differ-
ence between the two polymers is an alkoxy versus an al-
kane functional group neither of which is on the polymer
backbone.
Figure 4 Normalized fluorescence emission of P7 as a well-dissolved
solution in chloroform (0.01 mg/mL) (black line) and a nanoparticle sus-
pension in water (red line), (λex = 375 nm)
570 nm, which is a significant hypsochromatic shift (94
nm) compared to the nonaggregated form. The large Stokes
shift of P9 (223 nm) contrasts with the double Stokes shifts
for polymer P8 (due to the dual emission) of 38 and 287
nm. Additionally, P8’s larger ratio of 9,9-dioctylfluorene
monomer 4 compared to P9’s 1:1 monomer ratio results in
P8 having a polymer weight approximately 2.5 greater than
that of P9, while still displaying fluorescence properties
that are comparable to P9 in the aggregated state.
Figure 3 Normalized fluorescence emission of P2 as a well-dissolved
solution in chloroform (0.01 mg/mL) (black line) and as a nanoparticle
suspension in water (red line) (λex = 380 nm)
In addition to characterizing the polymer’s photophysi-
cal properties, all polymers were screened for their ability
to detect BPA, BPF, and BPS (compounds 1–3).38 The fluores-
cence modulation39 of the polymers in the presence of these
analytes was measured as both well-dissolved chloroform
solutions and as nanoparticles suspended in water. All poly-
mers demonstrated some degree of fluorescence modula-
tion in the presence of at least two bisphenols (Tables 3 and
4). The fluorescence response of P1, a previously reported
polymer, to all bisphenol analytes is included in the Sup-
porting Information for this manuscript.
All polymers demonstrated some degree of fluorescence
modulation when they were dissolved in chloroform; how-
ever, high analyte concentrations (1 mM) were required to
achieve measurable fluorescence responses. Moreover, poor
selectivity between structurally similar analytes was ob-
served, with half of the polymers, when dissolved in chloro-
form, displaying nearly identical modulation values with all
analytes investigated. Polmer P2 had one of the largest fluo-
rescence modulations as a chloroform solution with the ad-
dition of BPS, with a modulation value of 1.48 obtained
(Figure 5, a), whereas P6 was one of the most selective as a
chloroform solution, with noticeably different fluorescence
spectra obtained for all bisphenol analytes (Figure 5, b). Ad-
ditionally, P4 showed similar selectivity to that of P6 and a
similarly large fluorescence modulation to that of P2, with
Interestingly, P7’s fluorescence emission changed from
a spectrum with two emission maxima when dissolved in
chloroform to a spectrum with much greater fine structure
upon aggregation in nanoparticles, with four distinct maxi-
ma observed (Figure 4). The emission spectrum with four
maxima shows the same fine structure as the fluorescence
emission of naphthalene36 and has a bathochromic shift of
42 nm compared to the nonaggregated state, which sug-
gests J-aggregate formation.37 These spectral features
strongly suggest a geometric arrangement in which the
polymer chains stack in a staggered arrangement with the
pendant naphthalene moieties of P7 directly above and be-
low the fluorene backbone segments from neighboring
polymer chains.
Polymers P8 and P9 are comprised of the same mono-
mer units, albeit with different ratios of monomer in the
polymer product (P9: 1:1 monomer ratio; P8: 3:1 ratio of
9,9-dioctylfluorene to anthraquinone monomer, Figure 2).
Interestingly, P8 displays two emission maxima at 414 nm
and at 664 nm, while P9 has only one emission peak at 576
nm. In a well-solubilized polymer solution, the fluorescence
emission peak of P8 at 664 nm accounts for less than 10% of
the total fluorescence emission. However, similar to P2, the
aggregated form of P8 only displays one emission peak, at
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modulation values for P4 chloroform solution varying be-
tween 0.39 and 0.49. These fluorescence responses are
promising as the intermolecular forces that drive the bi-
sphenols to interact with the polymers are less prevalent in
chloroform solution than in aggregated states. Impressively,
linear discriminant analyses of the relatively minor changes
in spectral signals of the analyte–polymer complexes re-
sulted in 100% successful differentiation of highly structur-
ally similar analytes (Figure 6).
Figure 5 Normalized fluorescence emission of (A) P2 and (B) P6 as
Table 3 Fluorescence Modulation of Polymers Dissolved in Chloroform
with 1000 μM Bisphenola
well-dissolved chloroform solutions (0.01 mg/mL) with: no analyte
(black line), 1000 μM BPA (red line), 1000 μM BPF (green line), and
1000 μM BPS (blue line), (P2 λex = 380 nm, P6 λex = 340 nm)
Polymer
BPA
0.99
BPF
0.98
BPS
1.48
P2
P3
P4
P5
P6
P7
P8
P9
0.98
0.44
0.82
0.83
0.98
0.98
0.98
1.02
0.49
0.80
0.78
0.98
0.97
0.96
1.06
0.39
0.80
0.76
0.98
0.97
0.98
a 0.5 mL of 1000 μM bisphenol in chloroform added to 2.0 mL 0.01 mg/ml
polymer solution in chloroform. All modulation values were calculated ac-
37
cording to fluorescence modulation = Flanalyte/Flblank
.
Table 4 Fluorescence Modulation of Polymer Nanoparticles Suspend-
ed in Water with 50 μM Bisphenola
Polymer
BPA
1.03
BPF
1.05
BPS
1.04
P2
P3
P4
P5
P6
P7
P8
P9
Figure 6 Statistical array of polymers in chloroform solution with 1000
μM bisphenols
2.90
0.92
0.87
0.46
0.98
0.81
0.96
2.94
1.06
1.03
0.54
1.07
0.79
0.97
0.74
1.00
0.84
1.00
0.96
0.80
0.97
states, which increases the number of analyte binding sites
that the exciton samples prior to relaxation to the ground
state.40 The enhanced fluorescence modulation is seen with
nearly all polymer nanoparticles–analyte combinations, ex-
cept P4 and P6 with BPS, and current efforts in our labora-
tory are focused on elucidating reasons for the aberrant be-
havior of these particular combinations. Particularly nota-
ble fluorescence modulation is seen with polymer P3 and
P5 nanoparticles (Figure 7). Polymer P3 demonstrates the
most pronounced fluorescence modulation of all nanopar-
ticles, whereas P5 has the greatest selectivity of all
nanoparticle solutions between the less bulky BPF and the
bulkier BPS and BPA. The difference in the selectivity of
these polymers suggests that the electron-rich P3 is inter-
acting with the BPs primarily through electronic comple-
mentarity, whereas the fluorescence responses of P5 are
likely due to sterically driven interference between P5’s
side chains and the BP analytes that disrupts the polymer
aggregation.41 Furthermore, when the fluorescence emis-
a 0.5 mL of 50 μM bisphenol in water added to 2.0 mL nanoparticle solution
in water. All modulation values were calculated according to fluorescence
37
modulation = Flanalyte/Flblank.
While the chloroform solutions demonstrated sufficient
fluorescence modulation to differentiate between the bi-
sphenols at high concentrations, the polymer nanoparticles
had markedly enhanced selectivity to the bisphenol ana-
lytes at far lower analyte concentrations. This greater selec-
tivity is driven by hydrophobic aggregation of the bisphe-
nols with the polymer nanoparticles and the higher pro-
pensity for interpolymer exciton migration in aggregated
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sion of the nanoparticles in the presence of the analytes
was analyzed by using linear discriminant analysis (Figure
8), 100% differentiation between the three bisphenols at
low concentrations (50 μM) was obtained. Finally, the sta-
bility of the nanoparticles in water was observed over 72
hours by DLS and no significant degradation or precipita-
tion of the nanoparticles was observed. This is consistent
with literature reported longevity studies of conjugated
polymer nanoparticles generally remaining stable for
weeks in aqueous solution.42
fluorescence emission in aggregated states (i.e. in nanopar-
ticles) compared to their fluorescence emission profiles as
well-dissolved solutions in chloroform. The fluorescence re-
sponses of the polymers to the addition of BPA, BPF, and BPS
were investigated, both for well-dissolved polymer solu-
tions and as aggregated polymer nanoparticles. The poly-
mers demonstrated some degree of fluorescence modula-
tion in the vast majority of polymer–analyte parings with
isolated analyte–polymer pairs demonstrating little to no
observed modulation. With use of linear discriminant anal-
ysis, these distinctive fluorescence responses could differ-
entiate between the three bisphenols with 100% selectivity,
even among highly structurally similar analytes. Efforts to-
wards extending this fluorescence-based detection system
to other common environmental toxicants as well as evalu-
ating the use of polymeric thin films for such sensing appli-
cations are currently underway in our laboratory. Further
efforts towards determining the selectivity and robustness
of this system by evaluating the system in complex aqueous
media and expanding the analyte scope to other aromatic
compounds both with and without bisphenols as competi-
tive analyte studies will be performed, and the results of
these and other investigations will be reported in due
course.
Figure 7 Normalized fluorescence emission of (A) P3 and (B) P5 as
nanoparticles suspended in water with: no analyte (black line), 50 μM
BPA (red line), 50 μM BPF (green line), and 50 μM BPS (blue line) (P3
λex = 378 nm, P5 λex = 345 nm)
Funding Information
The authors acknowledge the University of Rhode Island chemistry
department for funding of this work.
)(
Acknowledgment
The authors thank Dr. Matthew Kiesewetter and Mr. Kurt Fastnacht at
the University of Rhode Island for the use of Dr. Kiesewetter’s Agilent
1260 Infinity II Multi-Detector GPC/SEC System. We would like to
thank Dr. William Euler for the use of his Malvern Zetasizer Nano ZS.
Supporting Information
Supporting information for this article is available online at
https://doi.org/10.1055/s-0037-1609946.
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References and Notes
Figure 8 Statistical array of polymer nanoparticles in water with 50 μM
bisphenols
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